FA Vit A

Question 1

How called vit A?

Answer 1

Retinol

Question 2

Inactive precursors (provitamins) of vit A?

Answer 2

Carotenoids (esp., alpha-carotene, beta-carotene, gamma-carotene)

Question 3

Activation of vit A?

Answer 3

carotinoid is cleaved into two retinal molecules; it can be reversibly reduced to retinol and reversibly oxidized to retinoic acid.

Question 4

vit A active forms?

Answer 4

Retinal, Retinoic acid

Question 5

4 groups of function of vit A?

Answer 5

Vision
Gene transcription
Tissue maintenance and cell differentiation
ANTIOXIDANT

Question 6

Vision. Vit. A is component of what?

Answer 6

Vision: component of rhodopsin as 11-cis-retinal

Question 7

Tissue maintenance and cell differentiation. What is vit A form?

Answer 7

Mainly retinoic acid

Question 8

vit A on differentiation of tissues?

Answer 8

Promotes differentiation of epithelium into specialized tissue (e.g., pancreatic cells and goblet cells (aka mucous secreting))

Question 9

vit A prevents of what? (tissues)

Answer 9

Prevents metaplasia of squamous cells

Question 10

vit A on gene trasncription. What substance binds its nuclear receptors?

Answer 10

All-trans retinoic acid (ATRA) binds to its nuclear receptors.

Question 11

what are retinoic acid receptors in nucleus?

Answer 11

Retinoic acid receptors, RAR; retinoid X receptors, RXR

Question 12

what happens when vit a rec. are activated in nucleus?

Answer 12

All-trans retinoic acid (ATRA) binds to its nuclear receptors (retinoic acid receptors, RAR; retinoid X receptors, RXR) → receptor dimerization → binding to DNA → uncoiling of chromatin → exposure of promoter regions of genes → binding of transcription factors to promoter → initiation of transcription and cell differentiation

Question 13

vit A regulates genes of what?

Answer 13

Regulation of various genes responsible for cell growth, cell differentiation, apoptosis, reproduction (e.g., spermatogenesis), and embryonic development

Question 14

what form of A is involved in vision?

Answer 14

Retinal is a major component of the retinal pigment rhodopsin in rods, which is necessary for vision.

Question 15

what form of vit A is involved in gene transcription and tissue maintenance?

Answer 15

retinoic acid and retinol are involved mainly in gene transcription and tissue maintenance.

Question 16

retinal is mainly for what function?

Answer 16

vision

Question 17

retinoic acid and retinol are mainly for what function?

Answer 17

gene transcription and tissue maintenance.

Question 18

source of vit A?

Answer 18

Plant sources: as inactive provitamin (esp. beta-carotene) in yellow and leafy vegetables (e.g., spinach, kale, carrots)

Animal sources: in storage form (e.g., in liver, kidney, fish, eggs, butter)

Question 19

storage of vit A?

Answer 19

In hepatic cells (Ito cells) within the perisinusoidal space (of Disse)

Question 20

storage form of vit A?

Answer 20

retinyl ester (e.g., retinyl palmitate)

Question 21

excretion of vit A?

Answer 21

Excretion: via bile and urine

Question 22

Deficiency of vit A. 2 groups of causes?

Answer 22

Disorders associated with fat malabsorption: inflammatory bowel disease (e.g., Crohn disease), celiac disease, cystic fibrosis, pancreatic insufficiency, cholestasis

Malnutrition: most common cause of vitamin A deficiency in developing countries

Question 23

what a states related to malabsorbtion for vit A?

Answer 23

inflammatory bowel disease (e.g., Crohn disease), celiac disease, cystic fibrosis, pancreatic insufficiency, cholestasis

Question 24

most common cause of vit A def. in developing countries?

Answer 24

malnutrition

Question 25

how is called night blindness?

Answer 25

nyctalopia

Question 26

MAIN visual clinical features of vit A def?

Answer 26

``` night blindness (nyctalopia); Retinopathy Xerophthalmia Keratomalacia Bitot spots ```

Question 27

what is keratomalacia?

Answer 27

corneal degeneration

Question 28

what are Bitot spots?

Answer 28

keratin debris; foamy appearance on conjuctiva. | Caused by squamous cell metaplasia and keratinization of the conjunctiva

Question 29

what causes Bitot spots?

Answer 29

Caused by squamous cell metaplasia and keratinization of the conjunctiva

Question 30

what 4 other manifestations of vit A deficiency?

Answer 30

Keratinizing squamous metaplasia of the bladder (pearl-like plaques on cystoscopy) Xerosis cutis Immunosuppression: Vitamin A deficiency increases the risk of a measles infection taking a severe course. Poor growth

Question 31

what is xerosis cutis?

Answer 31

dry, scaly skin

Question 32

causes of vit A excess?

Answer 32

increased intake via supplements or drugs

Question 33

vit A acute toxicity manifestation?

Answer 33

``` Nausea, vomiting Vertigo Fatigue Headache Blurred vision ```

Question 34

vit A chronic toxicity manifestation?

Answer 34

``` Alopecia Arthralgias Dry skin, scaling Hepatosplenomegaly, hepatic toxicity Pseudotumor cerebri ```

Question 35

VIT A IS TERATOGENIC. MANIFESTATION?

Answer 35

``` Facial anomalies: microcephaly, microphthalmia, and cleft palate Thymic agenesis Cardiovascular abnormalities Neurodevelopmental disability Fetal death ```

Question 36

what to do before prescribing isoretinoin (vit a derivate) for women?

Answer 36

A negative pregnancy test and two forms of contraception are required before prescribing isoretinoin (a vit A derivate) to women.

Question 37

terapeutic use of vit A? 3 groups

Answer 37

Measles Skin conditions: acne Acute promyelocytic leukemia (APL)

Question 38

what form of vit A is used for severe and what for mild acne?

Answer 38

Severe cystic acne (e.g., nodulocystic) and rosacea: isotretinoin (13-cis-retinoic acid) per os Mild acne: topical vitamin A

Question 39

what form of vit A is used for acute promyeolocytic leukemia (APL)?

Answer 39

all-trans retinoic acid (ATRA)

Question 40

why give vit a in measles?

Answer 40

Vitamin A should be given to measles patients with vitamin A deficiency to boost their immune system and reduce the risk of complications and mortality, especially in countries where vitamin A deficiency is endemic.